Download

Description/Abstract

Nuclei from human cells, stripped of their nuclear envelope by non-ionic detergent, contain a pool of endonuclear phospholipid that is distinct from that of other cellular membranes (Hunt et al., 2001 A. Hunt, G. Clark, G. Attard and A. Postle, J. Biol. Chem. 276 (11) (2001), pp. 8492–8499. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (52)Hunt et al., 2001). The composition dynamics, organisation and role of this endonuclear phospholipid are currently unclear, although there is mounting evidence of its possible involvement in the regulation of nuclear processes such as transcription (Martelli et al., 2004).

We have conducted a study that correlates the composition of endonuclear phospholipid to the DNA replication cycle. Using tandem electrospray ionisation mass spectrometry, the phospholipid content of cultured HeLa (human cervical carcinoma) cells and their isolated naked nuclei has been determined quantitatively, both in the presence and absence of cell-cycle blocking agents such as mimosine (Krude, 1999). By harvesting nuclei at different times during the blocking procedure, or after release of the block we were able to monitor the endonuclear phospholipid composition throughout the cell cycle.

Preliminary results indicate that the endonuclear lipid pool is enriched in diacyglycerol (DAG) compared with exonuclear lipids. The endonuclear DAG is also found to be enriched in saturated species. The potential implications of these observations on the cell-cycle dependence of lipid biosynthesis and on apoptosis are discussed.